at the airport, he was arrested by the police.
| A．When arrived | B．As arrived |
| C．At arriving | D．On his arrival |
Scientists ____ thousands of chemicals before they decided on the right one in the end.
| A．tried out | B．found out | C．worked out | D．turned out |
The deserted island is only _______ by boat.
| A．suitable | B．practical | C．available | D．accessible |
As is widely acknowledged, a great number of traffic accidents ____ numerous deaths and countless property loss all over the world every year.
| A．depend on | B．contribute to | C．result from | D．aim at |
To their great _____, Tom’s problem proved not to be as serious as they had feared.
| A．happy | B．worry | C．anxiety | D．relief |
________ we had read your letter _____the true state of affairs.
| A．It was until… that we understood | B．It was not until…that we understood |
| C．Until …did not we understand | D．Not until… we understood` |